This invention relates to small-size electronic calculators and more particularly to such calculators in which the characters are indirectly entered in the calculator keyboard.
The present invention, while of general application, is particularly well suited for use as a wrist-watch or similar size calculator which may or may not also provide an indicia of time. As is well known, the so-called pocket calculators in use at the present time for the most part are of the direct entry type, that is, the calculator contains a separate input key for each different digit and function to be entered in the calculator logic. Such calculators commonly include eleven digit keys, one for each of the digits "0" to "9" plus a decimal point, and a plurality of function keys for such mathematical functions as addition, subtraction, multiplication, division, equals, etc.
Other types of calculators proposed heretofore utilize an indirect entry form of keyboard. In these latter calculators the number of keys is less than the number of digits and functions for which the calculator is designed, and the keyboard includes a shift or stepping key to advance the calculator display until the desired digit or function is reached.
Heretofore, attempts to further miniaturize electronic calculators have exhibited several disadvantages. Of particular moment has been the attendant reduction in size of the individual keys on the calculator keyboard with the result that the keys were no longer readily operable through the use of a finger but required a pencil or other sharp implement to depress the keys sufficiently to enter the desired data. The problem manifested itself not only with direct entry calculators but also for calculators of the indirect entry type, and the available space for sixteen, eight or even four keys on the keyboard dictated the use of keys that were too small for many applications. In addition, particularly the indirect entry calculators were unnecessarily complicated in operation and required an excessive amount of time to perform the stepping and other functions necessary to select the desired data and to enter the selected data in the calculator logic. These various difficulties were experienced not only with prior calculators for performing conventional arithmetic functions but also with so-caled language or dictionary calculators and in other cases in which information was stored and acted upon through the use of a keyboard-type input.